The amount of cross-sectional area narrowing by atherosclerotic plaque in each 5-mm segment from the entire lengths of the right, left anterior descending and left circumflex coronary arteries and the size, predominant location and extent of myocardial scarring were determined in 59 necropsy with a healed transmural infarct (MI). The mean number of the 4 major epicardial coronary arteries narrowed severely (76-100% in cross-sectional area) was 3.0 in the 37 patients with posterior MI and 2.6 in the 22 patients with anterior MI (p less than .025). The mean percent of 5-mm segments narrowed severely from all 4 major coronary arteries was similar in the anterior and posterior MI groups (38%-vs-46%). The patients with anterior MI, however, had a higher percentage of 5-mm segements of the left anterior descending severely narrowed than of the left circumflex but not the right coronary artery (46%-vs-25% (p less than .001) and 40% (ns)). The patients with posterior MI had a higher percentage of segments of the right and left circumflex coronary arteries severly narrowed than of the left anterior descending (55% and 51%-vs-32%) (p less than .05).